1. Field of the Invention
The present invention relates to a method of manufacturing a toner.
2. Description of the Related Art
A toner that visualizes a latent image is used for various image formation processes, and for example, is used for an electrophotographic image formation process.
In an image forming apparatus utilizing an image forming process of an electrophotographic system, in general, a desired image is formed on a medium by executing a charging step of uniformly charging a photosensitive layer on the surface of a photoreceptor drum which is a latent image bearing member; an exposure step of projecting signal light of an original image onto the surface of the photoreceptor drum in a charged state, thereby forming an electrostatic latent image; a development step of supplying an electrophotographic toner to the electrostatic latent image on the surface of the photoreceptor drum, thereby achieving visualization; a transfer step of transferring the toner image on the surface of the photoreceptor drum onto a medium such as paper or an OHP sheet; a fixing step of fixing the toner image onto the medium by heating, applying a pressure or the like; and a cleaning step of removing the toner or the like which remains on the surface of the photoreceptor drum after toner image transfer by a cleaning blade, thereby achieving cleaning. There may be the case where the transfer of the toner image onto the medium is carried out via an intermediate transfer medium.
A developer which is used for such an image forming apparatus includes a one-component developer containing only a toner as a major component and a two-component developer to be used upon mixing a toner and a carrier.
Also, the toner which is used for such a developer is manufactured by a polymerization method represented by, for example, a kneading pulverization method, a suspension polymerization method or an emulsion polymerization cohesion method. In the kneading pulverization method, the toner is manufactured by melt-kneading a toner raw material containing a binder resin and a colorant as major components and having optionally a release agent, a charge control agent, etc. added and mixed therein, cooling it for solidification and then pulverizing and classifying the solid.
Recently, much efforts are underway in various technical fields in terms of global environment conservation. Materials of many products are currently manufactured from oil, however, energy is needed at the time of manufacturing and incineration of these materials, and carbon dioxide is generated. It is much important as a global warming countermeasure to make efforts at reduction of such energy, carbon dioxide, and the like.
Energy saving as the global warming countermeasure has been considered from various angles, and in an electrophotographic field, reduction of fixed energy by lowering a fixed temperature of a toner transferred onto a medium such as paper or an OHP sheet is effective. On the other hand, further increase in speed of a copier and a fax is desired, and the toner is absolutely needed for having a low-melting point.
As a method of fixing a toner image which has been transferred onto a medium such as paper or an OHP sheet, there is often adopted a contact heating-type fixing system for heat melting a toner image by a heating roller or the like and fixing it upon applying a pressure. Fixability of the toner in this system can be evaluated by a fixable temperature width of from a lower limit temperature of fixation to a hot offset initiation temperature. The realization of a low melting point of the toner as referred to herein is to decrease the lower limit temperature of fixation, whereby realization of low-temperature fixation can be achieved.
As a binder resin for the toner, a resin having a cross-linked structure, a resin containing a high-molecular component and a low-molecular component, and the like, are used. For such binder resins, when a content of a cross-linked component or the high-molecular component is increased in order to improve high-temperature offset resistance, melt viscosity of the resin increases too much so that there is a possibility that low temperature fixation property of the toner becomes insufficient. On the other hand, when a content of the low-molecular component is increased in order to improve the low temperature fixation property, the melt viscosity of the resin decreases, however, elasticity of the toner is lowered, and the high-temperature offset resistance may be lowered as a result. Therefore, in order to satisfy the low-melting point and the offset resistance in a high temperature of the toner at the same time, design of the binder resin for the toner is particularly important.
Additionally, as a new effort toward reduction of carbon dioxide as the global warming countermeasure, enormous attention is focused on use of a plant-derived resource referred to as biomass. Carbon dioxide that generates at the time of burning of biomass is carbon dioxide in the atmosphere that is originally obtained by plant photosynthesis, and balance of carbon dioxide in the atmosphere is thus zero. Such a nature having no effect on increasing and decreasing of carbon dioxide in the atmosphere is referred to as carbon-neutral, and it is believed that use of carbon-neutral biomass does not increase a carbon dioxide amount in the atmosphere. Biomass materials that are manufactured from such biomass are referred to as names of a biomass polymer, biomass plastic, a nonpetroleum-based high-polymer material and the like, and such biomass materials are derived from a monomer as a raw material, referred to as a biomass monomer.
Such efforts are underway that biomass excellent in environment safety and which is a resource that works on suppression of increase of carbon dioxide is used also in the electrophotographic field.
For example, Japanese Unexamined Patent Publication JP-A 2009-98534 discloses a method of manufacturing a polyester resin for a toner that is obtained by condensation polymerization of an alcoholic component and a carboxylic acid component containing a reaction mixture with rosin derived from a pine and unsaturated carboxylic acid that are reacted each other.
However, there is a problem that the toner containing the polyester resin that is manufactured by the method disclosed in JP-A 2009-98534 is excellent in preservation stability, but has difficulty in increasing a degree of polymerization of the polyester resin due to a difference of reactivity between two carboxyl groups contained in a carboxylic acid component, and sufficient high-temperature offset resistance and durability are thus not able to be obtained.